Introduction: Although continuous regional arterial infusion (CRAI) of a protease inhibitor and an antibiotic may be effective in patients with severe acute pancreatitis, CRAI has not yet been validated in large patient populations. We therefore evaluated the effectiveness of CRAI based on data from a national administrative database covering 1,032 Japanese hospitals. Methods: In-hospital mortality, length of stay and costs were compared in the CRAI and non-CRAI groups, using propensity score analysis to adjust for treatment selection bias. Results: A total of 17,415 eligible patients with acute pancreatitis were identified between 1 July and 30 September 2011, including 287 (1.6%) patients who underwent CRAI. One-to-one propensity-score matching generated 207 pairs with well-balanced baseline characteristics. In-hospital mortality rates were similar in the CRAI and non-CRAI groups (7.7% vs. 8.7%; odds ratio, 0.88; 95% confidence interval, 0.44–1.78, P = 0.720). CRAI was associated with significantly longer median hospital stay (29 vs. 18 days, P < 0.001), significantly higher median total cost (21,800 vs. 12,600 United States dollars, P < 0.001), and a higher rate of interventions for infectious complications, such as endoscopic/surgical necrosectomy or percutaneous drainage (2.9% vs. 0.5%, P = 0.061). Conclusions: CRAI was not effective in reducing in-hospital mortality rate in patients with acute pancreatitis, but was associated with longer hospital stay and higher costs. Randomized controlled trials in large numbers of patients are required to further evaluate CRAI for this indication.